On 10/17/2012 10:46 AM, Greg Stark wrote:
>
> I dislike both of the explanations above which don't actually explain
> why people shouldn't use rules (Josh does say they're tricky which is
> a start). Just telling people we hate parts of the system doesn't
> really come off well and leaves them wondering why.
>
> I would suggest something like
>
> Warning: RULES are tricky to use correctly. They rewrite the original
> query into a new query before it is run and it is very hard to
> correctly anticipate and rewrite every possible input query into the
> desired result. There are also unexpected interactions with other
> components when RULES do something unexpected such as rewrite a single
> query to return two result sets.
>
> For most applications it's much simpler and more predictable to use
> TRIGGERs. ROW level triggers are evaluated for each row the original
> query is about to process (or has just finished processing) and this
> makes them much easier to follow. Statement level TRIGGERs can be used
> for audit logs and similar operations which need to run once per
> statement.
>
I am not sure where to stick it but we should also include the fact that
rules are almost always slower that a trigger/function comparative.
Sincerely,
JD
>
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